There is a difference between ki(chi, prana, unraw mana, qi) and psi (mind energy+thought energy). Ki is like the force that your spirit holds. It makes your spirit immune to things and your spirit feeds on it. Psi is mind energy or thought energy that are used for psionic techniques like psi beam and telekinesis.

Yes there is a little bit different. But all energy have it unique propeties. For example If you're using pyro then the energy mark is fire. And the opposite one for cyro. Despite the different, they're just energy. There's no need to point out just a little different between them to create many type of energy